1. Field of the Invention
The present invention relates to a design aid apparatus for aiding in design of placement of objects for a multilayer wiring board. The present invention in particular relates to techniques of aiding in separately designing different board portions which are set in a lamination direction of the multilayer wiring board.
2. Related Art
Conventionally, electronic devices which need to be made smaller in size are often implemented using multilayer wiring boards.
An advanced manufacturing technique in recent years makes it possible to produce multilayer wiring boards in which tiny components such as bare chip semiconductors are embedded (for example, see the news release article dated Sep. 9, 2002 by Matsushita Electric Industrial Co., Ltd. “Development of New 3-D Module “SIMPACT™”” (http://panasonic.co.jp/corp/news/official.data/data .dir/jn020909-1/jn020909-1.html). Such a manufacturing technique achieves a high degree of flexibility in placement of components to a multilayer wiring board, and significantly improves the packaging density, of the multilayer wiring board.
FIG. 40 shows a multilayer wiring board 2001 having components embedded therein, as one example. This multilayer wiring board 2001 has components 2201 and 2206 mounted on the board surfaces, and components 2202 to 2205 embedded inside.
A design aid apparatus capable of assisting in design of placement of components inside a multilayer wiring board is well known in the art (e.g. Japanese Patent Application Publication No. 2001-243271). By optimally placing components inside and on the board surfaces of a multilayer wiring board using such a design aid apparatus, the packaging density can be significantly increased, with it being possible to realize a smaller electronic device.
This method, however, has the following problem. When the multilayer wiring board has a greater number of layers, the degree of flexibility in placement of components increases. If the flexibility is excessively high, an enormous amount of time and effort is needed for a design operation even with the help of the above design aid apparatus.
In view of this, the following method has been proposed to design a multi layer wiring board. According to this method, the multilayer wiring board is separated into board portions in a lamination direction, and design of placement of components is performed separately for each board portion.
FIG. 41 shows a multilayer wiring board 3001 which is separated. by a boundary dielectric 3001 into board portions 3002 and 3003. This multilayer wiring board 3001 has components 3201 and 3205 mounted on the board surfaces, and components 3202 to 3204 embedded inside.
According to the above design method, the total design of the multilayer wiring board 3001 can be conducted through a partial design process and a boundary management process. In the partial design process, the board portions 3002 and 3003 are designed separately. In the boundary management process, the design of the board portion 3002 and the design of the board portion 3003 made in the partial design process are managed to be consistent with each other in relation to the boundary dielectric 3301.
Though not able to achieve an optimum packaging density, this design method treats fewer layers in each partial design process, thereby limiting the flexibility in placement of components. Also, the partial design process for the board portion 3002 and the partial design process for the board portion 3003 can be conducted in the form of division of labor, with it being possible to reduce the number of design steps and shorten the design time.
Here, embedment of components in each of the board portions 3002 and 3003 may be prohibited. In such a case, components are placed only on the surfaces of each of the board portions 3002 and 3003 in the partial design process. This further reduces the number of design steps.
Conventionally, the above design method is used in consideration of a desired packaging density and design time. Note here that a multilayer wiring board having board portions which are each prohibited from embedment of components can be produced using the aforementioned advanced manufacturing technique. Hence such a multilayer wiring board is equivalent to a multilayer wiring board in which components are not embedded in some of a plurality of dielectrics.
In the absence of a design aid apparatus for totally and effectively aiding in design of a multilayer wiring board according to the above design method, however, the following problem arises.
Suppose embedment of components in each board portion of a multilayer wiring board is prohibited. In this case, by using a design aid apparatus for aiding in design of placement of components only on board surfaces, each partial design process can be favorably performed in the form of division of labor. However, the boundary management process needs to be performed manually. In view of a significant increase in size of circuitry which is subjected to design in recent years, this method is no longer practical.
Alternatively, the whole multilayer wiring board may be designed as one unit, using the aforementioned design aid apparatus for aiding in design of placement of components inside a multilayer wiring board. According to this method, however, it is difficult to perform each partial design process in the form of division of labor, so that the effect of shortening the design time lessens. Further, the user is required to master the operation of such a design aid apparatus.